Definition: Fungi are eukaryotic organisms
comprising of moulds, yeasts, mushrooms and other similar
organisms. Among this group of organisms only about 0.1% are
human pathogens. The term mycosis is used to define
diseases caused by fungi.

Mycosis can be classified under 4
heads based on the portal of entry and site
of infetion.

Types of
mycosis:

Type

Pathophysiology

Route

Example

Superficial

Limited to keratinized tissues

Topical

T. pedis

Subcutaneous

Localised to subcutaneous tissues

Broken skin

Rhinosporidiosis

Systemic

Disseminated widely

Inhalation

Histoplasmosis

Opportunistic

Local / Disseminated

Cell mediated immunity compromise

Candida /
Mucormycosis

Fungal infections of nose and sinuses are
getting common these days. With increasing incidence of HIV
and other diseases like diabetes which compromise host
immunity it is no wonder that the incidence of fungal infections
involving nose and para nasal sinuses is on the rise. In
India the incidence of fungal sinusitis in immuno competent
patients is also showing a rise. This particular fact need
to be studied further.

Classification of fungal
sinusitis: There are 5 different types of fungal sinusitis
with differing pathophysiology and clinical presentation. They
include:

1. Acute fulminant invasive sinusitis

2.
Chronic invasive fungal sinusitis

3. Granulomatous invasive
fungal sinusitis

4. Fungal ball

5. Allergic fungal
rhino sinusitis

Recently one more group is added i.e.
Eosinophilic fungal rhinosinusitis.

Acute fulminant invasive sinusitis:
The whole duration of illness in these patients is just less than 4
weeks. These patients are mostly immunocompromised
individuals. The reduced immunity could very well be
a result of

a. Diabetes mellitus

b.
AIDS

c. Immunosuppressive medicines

d. Malignancy
causing immune suppression

The fungus commonly associated
with this infection belongs to Mucoraceae family or Aspergillus
family. If Mucor is involved then the lesion is
angioinvasive and destroys both bone and soft tissue. Patients
belonging to this group have high mortality rate. Extensive
surgical debridement of the lesion with removal of necrotic tissue
should be performed and must be followed with intravenous antifungal
medication i.e. amphotericin B. If possible the underlying
cause for immune compromise should also be addressed. Since
granulocytes are essential to combat this condition, granulocyte
infusions have been tried out with success after surgical
debridement.

Chronic invasive fungal
sinusitis: This condition is also known as Non
granulomatous chronic invasive fungal sinusitis. This
condition commonly afflicts patients with diabetis mellitus.
This disorder is characterised by low grade inflammation with tissue
necrosis. There is very little vascular invasion.
Granuloma formation which is common in these patients requires an
appropriate cell mediated immune response which is common in
diabetics. The duration of this disease is longer than 4
weeks (more than 6 weeks in some cases). Orbital
extension is common, causing proptosis. These patients can be
managed by wide surgical debridement, followed by systemic
intravenous antifungal drugs like amphotericin B.

Granulomatous invasive fungal
sinusitis: This condition is also known
as Indolent fungal sinusitis. These patients have an
intact cell mediated immune reponse. Clincially it is
virtually impossible to distinguish it from non granulomatous fungal
sinusitis. Histopathology will clinch the diagnosis. The
intact immune system of the patient limits the invasion to the
superficial mucosa. Granulomas could be seen surrounding the
fungal elements thus preventing their deeper invasion. The
granulomas could be seen surrounded by multinulceated giant cells,
eosinophils etc. Surgical debridement alone is sufficient to
cure these patients. Their intact immune system takes
over from now on.

Fungal
Ball: These mycetomas commonly present as
unilateral opacification of maxillary or sphenoid sinus.
The ethmoids and frontal sinuses are very rarely involved.
These patients are usually immunocompetent without evidence of
atopy. The fungal ball is composed of tightly packed hyphae
often from Aspergillus, Alternaria and P. boydii. Treatment is
mostly surgical removal of the fungal mass combined with
widenening of ostium there by increasing the ventilation of the
sinuses. Antifungal drugs are not indicated in
these patients.

These patients present with progressive
nasal obstruction, crusting, rhinorrhoea, and chronic
rhinosinusitis. These patients can also come with dramatic
symptoms like visual loss and total nasal obstruction.

Classically radiology shows unilateraly expansile lesion of
the sinuses associated with bony erosion. The mass
appears as heterodense due to the presence of metallic elements in
the fungal hyphae.

The mechanism of causation of
allergic fungal sinusitis is IgE mediated hypersensitivity to
fungal proteins especially to aspergillus.

Figure
showing CT of a patient with allergic fungal
sinusitis.

Note: Expansile lesion involving the right
maxillary sinus. Erosion of medial wall of maxilla,
the nasal cavity is filled with heterodense mass. The
septum is seen being pushed to the opposite side.

Eosinophilic fungal sinusitis:
This terminology was first suggested by Ponikau et al to explain the
pathogenesis of not only allergic fungal sinusitis but also of
chronic rhinosinusitis. This disorder is usually
bilateral. Using sensitive techniques he was able to
demonstrate the presence of fungal hyphae in 97% of cases with
chronic rhinosinusitis. Since he failed to demonstrate typical
type I allergic features like elevated IgE levels in sera he
classified these patients under this head since he was not able to
include them in the allergic fungal sinusitis group. He hence
suggested an alternative theory saying that chronic sinusitis
belonging to this group is caused by abnormal cell mediated response
to fungal proteins.

Pathophysiology of eosinophilic
fungal sinusitis:

In response to exposure to fungal proteins
allergic mucin is formed in the mucosa. This allergic mucin
attracts eosinophils from blood vessels. These eosinophils
surround fungal hyphae and secrete substances like Major basic
proteins and various interleukins.

Management of
eosinophilic fungal sinusitis include surgical removal of
polypi with creation of good antrostomy to improve ventilation of
the sinuses. Oral steroids are indicated in these patients to
prevent recurrence. Prednisolone is administered in doses of
0.1mg/kg/day in cylces of four days and is gradually tapered after 6
weeks. After tapering of oral steroids, topical nasal steriods
can be administered for a period of 6 - 9
months.